DESCRIPTION: Functional studies have demonstrated that two specific domains of the c-Myc protein are essential for cell transformation: the C- terminal 100 amino acids which encompass the DNA binding basic/helix-loop- helix/leucine zipper region (B/HLH/LZ), and a small 20 amino acid segment from the N-terminus (called Myc homology box II of MbII) that is conserved in all members of the Myc family of proteins. This project will address the function of MbII domain of c-Myc through an analysis of the nuclear proteins that bind to this region and which are also essential for the transforming activity of the oncoprotein. Previous studies have showed that dominant interfering alleles of the c-Myc protein form protein complex that are dependent on the integrity of MbII and hence correlate with nuclear factors that may be essential for c-Myc function. The specific aims are as follows: I. Analyze the function of a novel protein called TR-AP that binds to the essential MBII region of the c-Myc oncoprotein in vivo. Genetic evidence suggests that TR-AP is required for the transforming activity of c-Myc and hence is a critical effector of c-Myc function. It is hypothesized that the c-Myc/Max heterodimer recruits TR-AP to specific chromosomal sites to alter gene expression and/or chromatin structure. II. Analyze the function of the yeast homologue of human TR-AP (called TRA1) to determine the essential role that this gene plays in growth. Yeast strains deficient in TRA1 will then be used to conduct a genetic screen to identify human and yeast genes that can complement a loss-of- function mutation in TR-AP. These experiments offer a novel genetic approach toward an understanding of c-Myc function. III. Purify and clone a nuclear protein that can bind tightly to the N-Myc oncoprotein and which appear to bind specifically to N-Myc but not c-Myc. He will also conduct a systematic mapping of the functional domains of the N-Myc protein to correlate important regions with nuclear factor interactions.